Android scale animation

Scale the image 3 times bigger.
The first two params 1f, 3.0f says the width starts from the original length and ends with 3 times longer in length.
The secone two params 1f, 3.0f says the height starts from the original length and ends with 3 times longer in length.
The last two params ivWheel.getWidth() / 2.0f, ivWheel.getHeight() / 2.0f, indicates the povit point of the scaleing, in this case, the scaling goes from the center of the image and scale outwards.

ScaleAnimation scaleAnimation = new ScaleAnimation(1f, 3.0f, 1f, 3.0f, ivWheel.getWidth() / 2.0f, ivWheel.getHeight() / 2.0f);
scaleAnimation.setDuration(3000); // scale to 3 times as big in 3 seconds
scaleAnimation.setInterpolator(this, android.R.interpolator.accelerate_decelerate);
ivWheel.startAnimation(scaleAnimation);
scaleAnimation.setAnimationListener(new Animation.AnimationListener() {
    public void onAnimationStart(Animation animation) {
        Log.d("ScaleActivity", "Scale started...");
    }

    public void onAnimationEnd(Animation animation) {
        Log.d("ScaleActivity", "Scale ended...");
    }

    public void onAnimationRepeat(Animation animation) {

    }
});

activity_scale.xml, the layout file for the scale animation demo.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">
    <Button
        android:id="@+id/btn_rotate"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Scale"
        android:onClick="scale"/>
    <ImageView
        android:id="@+id/iv_wheel"
        android:layout_width="60dp"
        android:layout_height="60dp"
        android:layout_margin="100dp"
        android:layout_gravity="center"
        android:src="@drawable/wheel_image" />
</LinearLayout>

ScaleActivity.java, the activity file for the scale animation demo.

public class ScaleActivity extends AppCompatActivity {

    private ImageView ivWheel;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_scale);
        ivWheel = (ImageView) findViewById(R.id.iv_wheel);
    }

    public void scale(View v) {
        ScaleAnimation scaleAnimation = new ScaleAnimation(1f, 3.0f, 1f, 3.0f, ivWheel.getWidth() / 2.0f, ivWheel.getHeight() / 2.0f);
        scaleAnimation.setDuration(3000); // scale to 3 times as big in 3 seconds

        ivWheel.startAnimation(scaleAnimation);
        scaleAnimation.setAnimationListener(new Animation.AnimationListener() {
            public void onAnimationEnd(Animation animation) {
                Log.d("ScaleActivity", "Scale started...");
            }

            public void onAnimationRepeat(Animation animation) {

            }

            public void onAnimationStart(Animation animation) {
                Log.d("ScaleActivity", "Scale ended...");
            }
        });
    }

    /**
     * Constructor to use when building a ScaleAnimation from code
     *
     * @param fromX Horizontal scaling factor to apply at the start of the
     *        animation
     * @param toX Horizontal scaling factor to apply at the end of the animation
     * @param fromY Vertical scaling factor to apply at the start of the
     *        animation
     * @param toY Vertical scaling factor to apply at the end of the animation
     * @param pivotX The X coordinate of the point about which the object is
     *        being scaled, specified as an absolute number where 0 is the left
     *        edge. (This point remains fixed while the object changes size.)
     * @param pivotY The Y coordinate of the point about which the object is
     *        being scaled, specified as an absolute number where 0 is the top
     *        edge. (This point remains fixed while the object changes size.)
     */
    //    public ScaleAnimation(float fromX, float toX, float fromY, float toY,
    //                          float pivotX, float pivotY)
}

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